The Challenge of Cannabis testing using Hair

Screening people for drugs has become an increasingly common procedure. Recovering addicts, employees, potential employees and many other groups are regularly subjected to tests for drugs such as cannabis. The use of cannabis is quite prevalent in the UK and the rest of Europe. This presents a significant problem because while there is no danger of dying from a cannabis overdose, a person under its influence can still pose a danger to themselves and others.

One of the most common tests for cannabis is by using hair samples. The main compound that is produced after breaking down of cannabis can be found in low concentrations in hair samples. However, this poses another challenge. Hair is found outside the body and this leaves it exposed to whatever is in the environment. Therefore if a person was in an environment where other people were using cannabis, there is a good chance of the substance being detected in hair samples even if an individual was himself not smoking.

There have been cases where people have made similar claims and this brings about the need to use testing methods that can differentiate between active use of cannabis and passive exposure.


Laboratory Testing Guidelines

This problem is far from new and it’s with this in mind that the SoHT i.e. Society of Hair Testing, provided guidelines on the proper way for conducting a proper lab test to detect the presence of cannabis in hair. These four guidelines are:

  1. The hair sample should first and foremost be washed to remove external contamination. This is done to limit the probability that the detected cannabis is from passive exposure.
  2. The instruments used must have the necessary sensitivity to actually detect THC in the hair.
  3. THCCOOH is the product that is produced when THC is metabolized in the body. For the test for cannabis to be considered positive, this compound must be present because it will prove that the THC did in fact pass through the user’s system.
  4. Last but not least, the instruments used in the lab must actually have the sensitivity needed to detect THCCOOH beyond reasonable doubt.


Modern Testing Labs

If you need to conduct a test for cannabis on a hair sample, you should ensure that it’s done in a proper laboratory. The lab should outline their testing procedure and it should include washing of the hair to remove external contaminants before the actual test.

According to the SoHT, THCCOOH levels of as low as 0.2 pg/mg of hair should be detectable if the laboratory is using the correct equipment. This means that the lab will likely be using state-of-the-art equipment to carry out the tests.

You should also go to a laboratory that is accredited just to be sure. Accreditation means that the lab’s equipment and testing methods have all been scrutinized and have been found to be of the correct standard. Some labs will even go as far as getting certification from the International Organization for Standardization.


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